The technical field of this invention is the on-board detection of motor vehicle operating environments, and particularly the detection of a racetrack operating environment from vehicle dynamic behavior alone.
Some vehicles are designed to be operated in two operating environments: (1) on a racetrack and (2) off the racetrack on public roads. Such vehicles may have vehicle systems with a first desired mode of operation on a racetrack and a second desired mode of operation off-track. Although an operator switch can be provided for the operator to select the mode of operation on knowledge of the vehicle operating environment, it may be preferable to provide automatic operating environment sensing and switching by the vehicle itself, either alone or as a backup to operator switching. But an automatic system for switching vehicle operating behavior between on-track and off-track modes requires apparatus for detecting vehicle operation on a racetrack.
This invention provides a method and apparatus for detecting and signaling when a motor vehicle is operating on a racetrack. The method and apparatus determines whether the vehicle is in a high lateral acceleration state or a low lateral acceleration state and when the vehicle is maintaining a minimum speed. The method and apparatus increments a count when the vehicle is in the high lateral acceleration state if the vehicle has maintained the minimum speed for a first time since the last increment or decrement of the count and decrements the count when the vehicle is in the low lateral acceleration state if the vehicle has maintained the minimum speed for a second time since the last increment or decrement of the count. The method and apparatus detects and signals operation on a racetrack while the count exceeds a predetermined threshold count and otherwise detects and signals no operation on a racetrack. Racetrack driving is thus detected through repeated episodes of high lateral acceleration during high speed turns on racetrack curves and corners.
In a preferred embodiment, the method and apparatus of the invention includes a vehicle mounted accelerometer and a time accumulator repeatedly incremented while the magnitude of an output signal of the lateral accelerometer exceeds a predetermined lateral acceleration threshold and cleared when the magnitude of the output signal of the lateral accelerometer falls at least an offset value below the lateral acceleration threshold. A high lateral acceleration state is determined when the time accumulator has accumulated a total time greater than a reference accumulated time; otherwise a low lateral acceleration state is determined. This provides hysteresis and stability in the system.
In a preferred embodiment, the second time, for which low lateral acceleration must be maintained in order to decrement the count, has a first value when the vehicle speed is greater than a predetermined speed greater than a racetrack caution speed and a second value greater than the first value when the vehicle speed is less than the predetermined speed greater than a racetrack caution speed. This prevents loss of racetrack detection during caution periods on the racetrack, when vehicle speeds and lateral accelerations are lower than under full racing conditions, without unduly lengthening the time required to detect no racetrack after the vehicle leaves the racetrack.